Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 14, Issue 24, 23 November 1978
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Volume 14, Issue 24
23 November 1978
Lamb-wave device with three operation modes
- Author(s): Kohji Toda and Yoshinari Yamashita
- Source: Electronics Letters, Volume 14, Issue 24, p. 747 –748
- DOI: 10.1049/el:19780505
- Type: Article
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A new type of Lamb-wave device with three operation modes is proposed and demonstrated. The transducers in the device consist of three electrode groups. One of the two combinations of the two interdigital electrode groups and the earth electrode is for a reference signal, whereas another combination is used to feed three kinds of input signal. This device has an efficient performance in three operation modes.
X-band balanced mixer using evanescent-mode circuitry
- Author(s): Günther Begemann and Carl Peters
- Source: Electronics Letters, Volume 14, Issue 24, p. 748 –749
- DOI: 10.1049/el:19780506
- Type: Article
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An X-Band balanced mixer using evanescent-mode circuitry has been developed utilising a waveguide magic-T. It shows an available conversion loss of 4.4 dB and a noise figure of 5.6 dB including a 1.2 dB noise contribution from an i.f. amplifier at a radio frequency of 8.61 GHz. Image and sum frequency are largely independently tunable.
Optical-fibre loss for high-speed drawing
- Author(s): Katsuyuki Imoto and Masao Sumi
- Source: Electronics Letters, Volume 14, Issue 24, p. 749 –750
- DOI: 10.1049/el:19780507
- Type: Article
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The influence of high-speed drawing on optical-fibre losses is investigated. Transmission losses near the 0.85 μm wavelength remain about 3 dB/km for drawing speeds in the range 20–300 m/min. Lower OH-ion content and increased colouration are observed at higher speeds.
Electromagnetic response of an anisotropic cylindrical shell
- Author(s): James R. Wait
- Source: Electronics Letters, Volume 14, Issue 24, p. 750 –752
- DOI: 10.1049/el:19780508
- Type: Article
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A remarkably simple and novel solution is obtained for the fields induced in an anisotropic cylindrical shell that is located coaxially within a long solenoid. This could be the basis of a nondestructive measuring scheme for stranded wire rope.
p+–n hyperabrupt GaAs varactors grown by molecular-beam epitaxy
- Author(s): D.W. Covington and W.H. Hicklin
- Source: Electronics Letters, Volume 14, Issue 24, p. 752 –753
- DOI: 10.1049/el:19780509
- Type: Article
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Gallium-arsenide p–n junction hyperabrupt varactor diodes have been grown by molecular-beam epitaxy. Near the junction the donor profile at depth x tracked x−1.2. A capacitance ratio C0/C12 of 10 is observed for bias voltages of 0 and 12 V.
Planar stripe with waist/notch (swan) injection laser
- Author(s): T. Ikegami ; G. Iwane ; H. Kawaguchi ; K. Wakita
- Source: Electronics Letters, Volume 14, Issue 24, p. 753 –754
- DOI: 10.1049/el:19780510
- Type: Article
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This letter describes a novel planar stripe-geometry injection laser (termed the Swan laser), showing a single transverse and longitudinal mode operation, made by a simple fabrication method. This stripe geometry is composed of a main stripe section with a width of ≈10 μm and a mode-control section with a nominal width near the carrier diffusion length less than 5 μm; the shape looks like a waist/notch along the stripe. The kink of the light output does not appear at a power level of more than 20 mW/facet.
Fabrication of a m.o.s.f.e.t. with ‘spoxide’ as the gate dielectric having low interface state density
- Author(s): Utpal Kumar Chakrabarti
- Source: Electronics Letters, Volume 14, Issue 24, p. 754 –756
- DOI: 10.1049/el:19780511
- Type: Article
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Spin-on oxide (Spoxide), which forms part of the class of deposited oxides, has been found to produce a good electrical interface with silicon after HCl annealing, and surface-state densities of the order of 4 × 1010 eV−1 cm−2 are easily achievable. An n-channel depletion-type m.o.s.f.e.t. has been fabricated with Spoxide as the gate dielectric.
High-speed analogue multiplexer using s.a.w. technology
- Author(s): T.M. Reeder ; G.K. Montress ; T.W. Grudkowski
- Source: Electronics Letters, Volume 14, Issue 24, p. 756 –757
- DOI: 10.1049/el:19780512
- Type: Article
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A new type of high-speed analogue multiplexer is described that utilises surface-acoustic-wave (s.a.w.) technology. The device operation is based upon the conversion of P parallel analogue control inputs into a serial-output amplitude-modulated pulse train superimposed on a v.h.f. carrier. Experimental results are presented for a 10-channel prototype device with a sampling rate near 1 MHz and a modulation dynamic range exceeding 50 dB. The feasibility of achieving 100-channel operation at sampling rates up to 100 MHz is discussed.
Removal of the refractive index dip by an etching method
- Author(s): S. Hopland
- Source: Electronics Letters, Volume 14, Issue 24, p. 757 –759
- DOI: 10.1049/el:19780513
- Type: Article
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A new method for removing the refractive-index dip in a c.v.d.-fabricated fibre has been developed. The method gives reproducible results, and might be of practical interest in the production of optical fibres. The method can be applied for the fabrication of fibres with different dip diameters for experimental testing of theories.
High-power GaAs f.e.t. prepared by molecular-beam epitaxy
- Author(s): M. Wataze ; Y. Mitsui ; T. Shimanoe ; M. Nakatani ; S. Mitsui
- Source: Electronics Letters, Volume 14, Issue 24, p. 759 –761
- DOI: 10.1049/el:19780514
- Type: Article
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High-power GaAs field-effect transistors were fabricated on molecular-beam epitaxial GaAs crystals. Devices with a power output at 1 dB gain compression of 4.0 W, a corresponding linear gain of 5.4 dB and a power-added efficiency as high as 35% have been realised.
Spatial distribution of defects in SiO2
- Author(s): H.A. Mughal ; W. Eccleston ; R.A. Stuart
- Source: Electronics Letters, Volume 14, Issue 24, p. 761 –762
- DOI: 10.1049/el:19780515
- Type: Article
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Predictions of the yield of integrated circuits are at present based on the assumption that defects are distributed spatially over the surface of a silicon slice according to Bose-Einstein statistics. In this letter it is shown, by means of the liquid-crystal technique, that at least one type of defect which can occur in integrated circuits-the oxide defect-obeys Poisson statistics.
Class ab bipolar voltage-current convertor
- Author(s): M.K.N. Rao and J.W. Haslett
- Source: Electronics Letters, Volume 14, Issue 24, p. 762 –764
- DOI: 10.1049/el:19780516
- Type: Article
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A class AB voltage-current converter is described. The circuit is basically a modified version of Widlar's composite n-p-n transistor structure. 1, 2 The overall network combines extended drive-current capability with good small-signal properties over a useful frequency range.
Optimum profile parameter on graded-index optical fibre at 1.27 μm wavelength
- Author(s): Yasuji Ohmori ; Kazunori Chida ; Masaharu Horiguchi ; Iwao Hatakeyama
- Source: Electronics Letters, Volume 14, Issue 24, p. 764 –765
- DOI: 10.1049/el:19780517
- Type: Article
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The optimum profile parameter on germanium phosphosilicate graded-index optical fibres at 1.27 μm wavelength is examined experimentally and is found to be 1.88 ± 0.01. Graded-index optical fibres that simultaneously possess high transmission bandwidth (in excess of 1 GHz km) and attenuation below 1 dB/km are obtained.
New approach to stochastic data analysis: the Nile river at Aswan
- Author(s): O. Ibidapo-Obe
- Source: Electronics Letters, Volume 14, Issue 24, p. 765 –767
- DOI: 10.1049/el:19780518
- Type: Article
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An autoregressive model with Markovian assumption on the parameters (a.r.m.p.) is developed and utilised for the design of an adaptive system in the identification and estimation of stochastic plant parameters. The model is used as a prediction tool for the annual flows of the Nile river at Aswan. The algorithm shows that the a.r.m.p. offers certain advantages over existing modelling techniques.
Network model for strip-fed cavity-backed printed slot antenna
- Author(s): D.T. Shahani and Bharathi Bhat
- Source: Electronics Letters, Volume 14, Issue 24, p. 767 –769
- DOI: 10.1049/el:19780519
- Type: Article
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An equivalent network for the strip-fed cavity-backed slot antenna is derived. The model is based on some physical insight into the problem. The various parameters of the network are derived from the experimental data on the input reflection parameter of the antenna. This model gives an insight into the strip-slot-cavity coupling and hence the working of the structure. It is also useful for predicting the performance of such practical antennas.
Thermal-gradient enhanced current spreading in d.h. lasers
- Author(s): R.T. Lynch ; L. Yang ; R.Y. Hung
- Source: Electronics Letters, Volume 14, Issue 24, p. 769 –770
- DOI: 10.1049/el:19780520
- Type: Article
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The observed differences in light output against current (P/I) curves between c.w. and short-pulse operation of (GaAl)As lasers have generally been considered as arising from the increase in active-region temperature under c.w. operation. This temperature increase results in a decrease in optical output at a given current level because of the reduced carrier confinement at the heterojunctions. However, by carefully compensating the temperature rise in the active region in the c.w. mode, we have experimentally established that, for exactly the same active-region temperature and total pumping current, the laser emits significantly less light in the c.w. mode than in the pulse mode of operation. This difference becomes larger as the input power increases. The thermoelectric (Seebeck) effect can explain this observation. The temperature gradient induced by c.w. operation causes current to flow away from the stripe region, leading to excess wasted current and reduced light output.
Adaptive cancellation of crosspolarisation: experiments with unmodulated signals
- Author(s): P. Delogne and P. Sobieski
- Source: Electronics Letters, Volume 14, Issue 24, p. 770 –772
- DOI: 10.1049/el:19780521
- Type: Article
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An experiment on the adaptive cancellation of crosspolarisation is reported. The measurements were performed on a 2.2 km long horizontal link at 12 GHz using linear polarisations. The cancellation system proved to be very efficient even for the most severe meterological events.
Statistical design centring for electrical circuits
- Author(s): R.S. Soin and R. Spence
- Source: Electronics Letters, Volume 14, Issue 24, p. 772 –774
- DOI: 10.1049/el:19780522
- Type: Article
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The problem of maximising the manufacturing yield of electrical circuits is addressed. Within the constraint that the absolute component tolerances and the forms of their statistical distributions are fixed, a new design-centring procedure is developed and illustrated by example. It is directly applicable to the design of discrete circuits where fixed tolerances are often considered. The assumption of fixed tolerances also suggests its relevance (as yet untested) to the design of integrated circuits.
Note on the stability of first-order p.w.m. systems
- Author(s): R. Unnikrishnan
- Source: Electronics Letters, Volume 14, Issue 24, p. 774 –775
- DOI: 10.1049/el:19780523
- Type: Article
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It is shown in this letter that the necessary and sufficient condition for stability of first-order pulse-width-modulated (p.w.m.) systems derived using exact analysis by Skoog and Blankenship1 is the same as that obtained by using a linearisation technique. This points to the accuracy of the linear model which is simple and easy to use.
Laser level-control circuit for high-bit-rate systems using a slope detector
- Author(s): D.W. Smith
- Source: Electronics Letters, Volume 14, Issue 24, p. 775 –776
- DOI: 10.1049/el:19780524
- Type: Article
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An automatic level-control circuit for semiconductor laser diodes has been developed for use in a 140 Mbit/s fibre system. The circuit has low power consumption and has the potential for operation at high bit rates.
Axial-line-current approximation for short cylindrical wires
- Author(s): R. Neri and T.S.M. Maclean
- Source: Electronics Letters, Volume 14, Issue 24, p. 776 –778
- DOI: 10.1049/el:19780525
- Type: Article
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A commonly used approximation in calculating the self impedance of a short cylindrical wire is to assume that current flows along its axis only. Numerical results are presented that quantify the error in the vector potential arising from this line-current assumption for small length/diameter ratios of the wire, provided that the skin depth is very much less than the wire radius.
Improved adaptive observer with optimal convergence
- Author(s): C.K. Li
- Source: Electronics Letters, Volume 14, Issue 24, p. 778 –779
- DOI: 10.1049/el:19780526
- Type: Article
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A simple technique for simultaneous parameter identification and state estimation of linear discrete systems is presented. The gradient method is used for identification and the global stability of the scheme is guaranteed by the use of Lyapunov's method. The optimal adaptive gains are also considered for more rapid convergence.
Analysis of the effect of spontaneous-emission coupling on the number of excited longitudinal modes in semiconductor lasers
- Author(s): D. Renner and J.E. Carroll
- Source: Electronics Letters, Volume 14, Issue 24, p. 779 –781
- DOI: 10.1049/el:19780527
- Type: Article
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Normalised multimode rate equations are used to relate the number of lasing modes and the spontaneous-emission coupling coefficient. An almost linear relationship is found for ideal injection lasers with no reflections other than those of the end facets. The effect of small variations in mode losses is also discussed.
Submicrosecond X-ray lithography
- Author(s): D.J. Nagel ; M.C. Peckerar ; R.R. Whitlock ; J.R. Greig ; R.E. Pechacek
- Source: Electronics Letters, Volume 14, Issue 24, p. 781 –782
- DOI: 10.1049/el:19780528
- Type: Article
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X-rays from laser-heated plasmas were used to replicate features as fine as 750 nm in the positive resist polybutene-1-sulfone (p.b.s.). The measured sensitivities of p.b.s. to pulsed and d.c. X-rays (≈ 109 ratio in exposure rate) are similar (no reciprocity loss). Laser-plasma X-rays produced only small (0.25 V) flat-band shifts in m.o.s. capacitors at irradiation levels sufficient to expose p.b.s.
Fast s.a.w.-based discrete Fourier transformer
- Author(s): J.B.G. Roberts ; B.J. Darby ; R.A. Bale ; R. Eames
- Source: Electronics Letters, Volume 14, Issue 24, p. 783 –784
- DOI: 10.1049/el:19780529
- Type: Article
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Combining s.a.w. high-bandwidth filtering with digital data storage allows a digital d.f.t. to be computed very rapidly though with limited accuracy. A prime algorithm processor is described, using a s.a.w. filter interfaced with digital input/output, which dissociates the high but fixed speed of analogue computation from real data rates.
Thermal strain effects of acoustic surface waves in layered media
- Author(s): Kazuhiko Yamanouchi ; Morio Ishii ; Kimio Shibayama
- Source: Electronics Letters, Volume 14, Issue 24, p. 784 –786
- DOI: 10.1049/el:19780530
- Type: Article
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The propagation characteristics of acoustic surface waves in layered media are described. The strains caused in the film by thermal expansion can significantly affect the temperature coefficient of delay and the dispersion curves of velocity. Computed results for an SiO2/LiTaO3 structure are compared with experimentally measured values.
Power-handling capability of GaAs m.e.s.f.e.t.s
- Author(s): E. Kohn
- Source: Electronics Letters, Volume 14, Issue 24, p. 786 –788
- DOI: 10.1049/el:19780531
- Type: Article
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The limits in output power and power gain are considered with and without a stationary dipole domain in the channel. It follows that c.w. power levels of 5 W/mm and power gains normalised on frequency as high as 60 dBGHz2 are possible for gate lengths of 1 μm.
Switched-capacitor simulation of grounded inductors and gyrators
- Author(s): B.J. Hosticka and G.S. Moschytz
- Source: Electronics Letters, Volume 14, Issue 24, p. 788 –790
- DOI: 10.1049/el:19780532
- Type: Article
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A possible method for the simulation of a grounded inductor and a grounded gyrator, by active switched-capacitor combinations, is presented.
Some proposals for improved forms of precision fast digital-analogue and analogue-digital convertors
- Author(s): J.R. Stockton and R.B.D. Knight
- Source: Electronics Letters, Volume 14, Issue 24, p. 790 –791
- DOI: 10.1049/el:19780533
- Type: Article
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Some proposed digitally adjusted fast d.a.c.s are described. These may be combined with the well known successive approximation principle to produce a.d.c.s with economical digital correction of their bit values. It becomes possible to envisage the self-adjusting fast a.d.c., capable of maintaining accurate linearity.
Some properties of nopower electronic circuits
- Author(s): G.M. Ettinger and L.T. Shooter
- Source: Electronics Letters, Volume 14, Issue 24, p. 791 –792
- DOI: 10.1049/el:19780534
- Type: Article
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The concept of nopower electronic circuits is explained, with special reference to c.m.o.s. logic. Performance of a range of nopower circuits including gates, counters, monostables and displays is described and applications are discussed.
Simple relationship between differential mode delay in optical fibres and the deviation from optimum profile
- Author(s): K. Petermann
- Source: Electronics Letters, Volume 14, Issue 24, p. 793 –794
- DOI: 10.1049/el:19780535
- Type: Article
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A very simple formula is given for determining the deviation of a given refractive-index profile from optimum after the differential mode delay has been measured.
Depolarisation of the linearly and circularly polarised 11.6, 11.8 and 14.5 GHz OTS signals
- Author(s): R.G. Howell ; J. Thirlwell ; R.R. Bell
- Source: Electronics Letters, Volume 14, Issue 24, p. 794 –796
- DOI: 10.1049/el:19780536
- Type: Article
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Severe depolarisation (attributed to ice particles) measured simultaneously using linearly (11.6 GHz) and circularly (11.8 GHz) polarised beacons from OTS and the 14.5 GHz circularly polarised up-path transmissions is reported. Concurrent 12.1, 14.8, 20 and 30 GHz radiometer results are also presented, and it is noted that backscattered energy from the 14.5 GHz transmissions has interfered with the 14.8 GHz radiometer, producing an output that exhibits some correlation with the circular depolarisation.
Dielectric-constant step of InP/In1−xGaxAsyP1−y d.h. lasers
- Author(s): G.D. Henshall ; P.D. Greene ; G.H.B. Thompson ; P.R. Selway
- Source: Electronics Letters, Volume 14, Issue 24, p. 796 –797
- DOI: 10.1049/el:19780537
- Type: Article
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Measurements are reported of the far-field beam angle perpendicular to the junction for InP/In1−xGaxAsyP1−y double-heterostructure lasers as a function of active-region thickness between 0.15 and 0.9 μm. The lasers operated with wavelengths close to 1.15 μm. Calculations show that good agreement between the theory and the experimental results is obtained using a dielectric-constant step δɛ between the InP and the In1−xGaxAsyP1−y of 0 75.
Electronics Letters Premium
- Author(s): E.A. Ash and P.J.B. Clarricoats
- Source: Electronics Letters, Volume 14, Issue 24, page: 798 –798
- DOI: 10.1049/el:19780538
- Type: Article
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